The present invention relates to a channel switching system for use in a digital communication system having one standby channel for N regular channels (1:N, N being a positive integer), and more particularly to a channel switching system for use in a digital communication system having a repeater station linked between two terminal stations and having a regenerative relay channel and a dropping/insertion channel for regular channels of the repeater station.
Usually, such a channel switching system consists of two terminal stations and a repeater to relay the transmission and reception of digital signals between the terminal stations. Each such station has a control device for switching over between regular and standby channels or routes to provide stable communications. In the repeater station of such a system, it has been customary to provide those digital channels needing no dropping and/or insertion, as in the case of a regenerative relay, with a digital code processing unit or with a modulating-demodulating circuit and a digital code processing unit, as will be described hereinafter, and to construct them in the same way as those which do require dropping and/or insertion. This technique is disadvantageous in that the repeater station is costly. The per channel cost in such a system can be reduced by constructing the regenerative relay channels at the repeater station without a digital code processing circuit or the like. However, if both regenerative relay circuits with dropping/insertion circuits having digital code processing circuits and modulating-demodulating circuits are provided together in the same system, the conventional channel switching system cannot be simply applied for the reason to be explained below.